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I am putting a rollbar in my 71 duster built for the F.A.S.T. class. I am trying to figure out the lightest, legal bar I can put in.

From reading the rule book I can run 1 3/4" .083 chromoly bar hoop with same size d/s sidebar, no p/s sidebar and equal sized rear braces.
With a 1 1/4" .065 cross bar.

Anybody ever build a bar like this? Approx. weight? Difference in weight of mild steel?
I have 2x3 frame connectors through the floor that I imagine will give it all the stiffness it really needs, so the bar is really only to appease tech.

Thanks guys.

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I am putting a rollbar in my 71 duster built for the F.A.S.T. class. I am trying to figure out the lightest, legal bar I can put in.

From reading the rule book I can run 1 3/4" .083 chromoly bar hoop with same size d/s sidebar, no p/s sidebar and equal sized rear braces.
With a 1 1/4" .065 cross bar.

Anybody ever build a bar like this? Approx. weight? Difference in weight of mild steel?
I have 2x3 frame connectors through the floor that I imagine will give it all the stiffness it really needs, so the bar is really only to appease tech.

Thanks guys.

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I'd worry about the 2X3 weight too if that was the big concern.
Go with something safe, and get the weight out in other places...

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https://board.moparts.org/ubbthreads/upload2/5595643-33.JPG
That is the exact Bar I put in my car because I am a weight fanatic!

I had to buy the cross bar separate since they included a 1-3/4" piece for the cross bar and they said they do not offer the 1-1/4".

I did not put the pieces on a scale, but just picking up the main hoop it was noticably lighter than I remember the .134 wall MS one I put in my Demon.

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If you were that concerned with weight, why the extra 2' of tubing on each of the rear braces? I'd have just gone with a straight tube and saved more weight than you did with the 1.25 bar.

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I am putting a rollbar in my 71 duster built for the F.A.S.T. class. I am trying to figure out the lightest, legal bar I can put in.

From reading the rule book I can run 1 3/4" .083 chromoly bar hoop with same size d/s sidebar, no p/s sidebar and equal sized rear braces.
With a 1 1/4" .065 cross bar.

Anybody ever build a bar like this? Approx. weight? Difference in weight of mild steel?
I have 2x3 frame connectors through the floor that I imagine will give it all the stiffness it really needs, so the bar is really only to appease tech.

Thanks guys.

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The main hoop, drivers bar, and back bars are about 25' of 1 3/4, and about 5' of 1 1/4 for the crossbar.

Weights of round tube - per foot:

Mild Steel .134 Wall D.O.M.
1 3/4 = 2.31lb 1 5/8 = 2.13lb 1 1/4 = 1.60lb

4130 Chrome Moly .083 Wall
1 3/4 = 1.47lb 1 5/8 = 1.37lb 1 1/4 = 1.03lb

4130 Chrome Moly .065 Wall
1 1/4 = .82lb

So the mild steel would be about 65 lbs total, and the Moly about 41 total.

Hope this helps....

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https://board.moparts.org/ubbthreads/upload2/5595643-33.JPG
That is the exact Bar I put in my car because I am a weight fanatic!

I had to buy the cross bar separate since they included a 1-3/4" piece for the cross bar and they said they do not offer the 1-1/4".

I did not put the pieces on a scale, but just picking up the main hoop it was noticably lighter than I remember the .134 wall MS one I put in my Demon.

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If you were that concerned with weight, why the extra 2' of tubing on each of the rear braces? I'd have just gone with a straight tube and saved more weight than you did with the 1.25 bar.

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2 totally different concepts! Those rear bars bend for 2 reasons other than saving weight. #1 I wanted a full interior and that allows you to retain the back seat. When you look in my car it has a nice full interior. #2, it saves room in the trunk. If those bars are straight I think they will end up going a lot farther back where they attach in the trunk floor. You are right it probably added 2 ft of length overall and a little weight. Which was necessary. Having a 1-3/4" cross bar is not.